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Compressing copies of CD tracks to use less disk space

A typical CD can hold several hundred megabytes (MB) of information. When copying CD tracks to your computer, you generally do not want to use as much disk space for the tracks as is available on the CD. To use less disk space, the Player can compress CD tracks when you copy them to your computer. However, some audio quality is lost when the track is compressed. The better the audio quality when a track is copied, the more disk space is required.

Windows Media Player automatically compresses CD tracks when you copy them to your computer; otherwise, one CD would use hundreds of megabytes on your computer. The Player uses codecs to compress tracks copied to your computer.

You can copy tracks as the following types of Windows Media Audio files:

Windows Media Audio. Tracks are copied using a constant bit rate. Depending on the music, the audio quality may not be the same throughout the track if certain sections of the audio are more complex and therefore harder to compress. However, this method provides you with a better estimate of the amount of space the track will require on your computer.

The following table shows the approximate disk space used for different audio qualities available for Windows Media Audio.

Quality	Bit rate*	Disk space per 650 MB or 74-minute CD**
Smallest size	48 kilobits per second (Kbps)	22 megabytes (MB)
Small	64 Kbps	28 MB
Medium	96 Kbps	42 MB
Medium-high	128 Kbps	56 MB
High	160 Kbps	69 MB
Best quality	192 Kbps	86 MB

*Bit rates are approximations.

**Refers to the amount of disk space required if you copy an entire CD according to quality level.

Windows Media Audio (variable bit rate). Tracks are copied using a variety of bit rates to compress the music as necessary. By using a variable bit rate, the Player can use more compression for audio sections that are easy to compress and less compression for audio sections that are harder to compress. A higher bit rate is used for more complex data and a lower bit rate is used for less complex data. The end result is a track that has a more consistent audio quality throughout. Tracks copied using Windows Media Audio (variable bit rate) may have a better audio quality, but require less disk space than a file copied using Windows Media Audio. Before you copy a track, there is no way to tell exactly how much disk space the track will require on your computer.
The following table shows the approximate range of disk space used for different audio qualities available for Windows Media Audio (variable bit rate).

Quality	Bit rate*	Disk space per 650 MB or 74-minute CD**
Smallest size	40 to 75 kilobits per second (Kbps)	40 to 75 megabytes (MB)
Small	50 to 95 Kbps	22 to 42 MB
Medium	85 to 145 Kbps	37 to 63 MB
High	135 to 215 Kbps	59 to 94 MB
Best quality	240 to 355 Kbps	105 to 155 MB

*Bit rates shown are approximations.

**Refers to the amount of disk space required if you copy an entire CD according to quality level.

Windows Media Audio Lossless. Tracks copied using Windows Media Audio Lossless should have the same audio quality as the track on the CD. If you have unlimited disk space, you may want to use Windows Media Audio Lossless. When you select this format, the audio quality slider is not available. You can only play tracks encoded using Windows Media Audio Lossless on computers. The tracks can be copied to portable devices, but Player converts the tracks to a much smaller size before they are copied to the portable device.
Audiophiles can use Windows Media Audio Lossless to archive CDs for efficient storage and to have the highest quality copy from which to make other copies. Tracks encoded with Windows Media Audio Lossless can also be used to create High-performance Media Access Technology, or HighMAT, CDs.

Note that Windows Media Audio Lossless is only available on select versions of Windows. For more information, see Special features.

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Compressing copies of CD tracks to use less disk space

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